ESE's works engine tuner

[Henk]

Haven't seen a two stroke on shell bearings. Doesn't mean it hasn't been done.

[Drew]

Haven't seen a two stroke on shell bearings. Doesn't mean it hasn't been done.

The biggest downside would have to be the volume I would have thought.

Unless the fickle bitch that is a two stroke tune and the narrow spread of power, means that there's no point in making one rev that high of course.

Was just a musing of course, I figure that if one could get a GT125 to rev past 15,000RPM it could have oodles of power extracted from it and still run a silly little 17mm carb per slug...But although I've read this thread, there's a lot I'm sure I didn't retain/understand.

[pete376403]

Not that you're ever likely to see one in a bucket, but, uniflow two stroke (eg GM) diesels run plain bearing cranks with high pressure lubrication. They also have cams, pushrods, poppet valves in the cylinder head and are still a two stroke.

[Drew]

Not that you're ever likely to see one in a bucket, but, uniflow two stroke (eg GM) diesels run plain bearing cranks with high pressure lubrication. They also have cams, pushrods, poppet valves in the cylinder head and are still a two stroke.

You forgot to mention forced induction. Can't even start one of those bad boys without pressure in the inlet tract.

They don't breath/burn the crank lubricant either, so it's not really relative to my question.

[husaberg]

Haven't seen a two stroke on shell bearings. Doesn't mean it hasn't been done.

Villiers used to run plain bushes.......not saying it was clever though

[WilDun]

Villiers used to run plain bushes.......not saying it was clever though

Yeah, so did British Seagull (outboards), Iron Horse (johnson outboards and lawnmower engines) and various others (including model aircraft engines). - The secret? 1 pint of oil to 1 gallon of petrol (think that's 8:1) and massive clouds of smoke!!

However, having said that, there have been many successful two stroke diesels with overhead valves and blowers which didn't use the crankcase as a pump, so really the same bottom ends as the four strokes.

Also, I remember one attempt at using overhead valves on an Italian two stroke kart engine - the overhead camshaft ran at half crank speed and the valves opened alternately (to prevent 'valve float' which would have happened if they opened at every crank revolution). I still think it used crankcase compression though, so no plain bearings.
Needless to say it didn't last long! - I haven't found it on the net.so far.

Trouble is, when you start adding all these things, then the weight, the complexity and the price also go up!
Let's just stick to the good old "simple" two stroke I say. Only problems it's got are pollution, exhausts bigger than the motor, high fuel consumption and it pisses off the Harley boys - nothing to worry about really!

[WilDun]

On the other hand, here's one for you four stroke boys, (and this has been successfully done on YS model aircraft four stroke engines), why not get "free" supercharging from having a crankcase charged four stroke? ie using a needle roller crank and a petroil mixture.
The piston will produce crankcase compression on each revolution of course, so on a single, every other stroke the charge will be stored in a small chamber in the head near the inlet valve and released when the inlet valve opens to accept the charge on the next stroke - really a four stroke top end on a two stroke bottom end.

I might also add that a on four stroke twin either boxer or parallel, (ie with 360 deg crank on a parallel twin, or a 180 deg crank on a boxer), whatever, but with both pistons hitting TDC at the same time and alternate firing), the necessity for a "storage chamber would disappear! - where have all those CB 125T bikes gone??
Maybe FLETTNER would be interested.
It actually does work, but of course for bucket racing it might be banned I dunno! - could just give you four stroke boys a fighting chance though!

Gotta get to bed, I might be hallucinating, then again I might not!

[mr bucketracer]

On the other hand, here's one for you four stroke boys, (and this has been successfully done on YS model aircraft four stroke engines), why not get "free" supercharging from having a crankcase charged four stroke? ie using a needle roller crank and a petroil mixture.
The piston will produce crankcase compression on each revolution of course, so on a single, every other stroke the charge will be stored in a small chamber in the head near the inlet valve and released when the inlet valve opens to accept the charge on the next stroke - really a four stroke top end on a two stroke bottom end.

I might also add that a on four stroke twin either boxer or parallel, (ie with 360 deg crank on a parallel twin, or a 180 deg crank on a boxer), whatever, but with both pistons hitting TDC at the same time and alternate firing), the necessity for a "storage chamber would disappear! - where have all those CB 125T bikes gone??
Maybe FLETTNER would be interested.
It actually does work, but of course for bucket racing it might be banned I dunno! - could just give you four stroke boys a fighting chance though!

Gotta get to bed, I might be hallucinating, then again I might not!

after thinking of the idea 20 or so years ago i found a speedway guy had done it to his engine. sounded like it did not work to good but may not of done it propery.. i dont think it would be aloud anyway been a form of supercharging

[WilDun]

after thinking of the idea 20 or so years ago i found a speedway guy had done it to his engine. sounded like it did not work to good but may not of done it propery.. i dont think it would be aloud anyway been a form of supercharging

Yeah, I thought that might be the case, but as we all know these things need a lot of hard work and fine tuning. It can work of course and it would be interesting to try but in this life we are restricted by rules wherever we turn. In saying that.
Buckets are a great outlet for experimentation but in order to keep things cheap and available to all, we have to have some rules I guess!
All just food for thought of course............How about an 'experimental and developmental only' class??

[Ocean1]

The piston will produce crankcase compression on each revolution of course, so on a single, every other stroke the charge will be stored in a small chamber in the head near the inlet valve and released when the inlet valve opens to accept the charge on the next stroke

Every stroke: Reeds at the base of the transfer ports.

. i dont think it would be aloud anyway been a form of supercharging

Which begs the question, why should 2 strokes be allowed the very same method?

[WilDun]

Every stroke: Reeds at the base of the transfer ports.

Which begs the question, why should 2 strokes be allowed the very same method?

We are talking four strokes here of course and having to store the charge for one revolution (in the case of a single, - twin is different) - two strokes don't have to store it although I guess they do exactly that in the exhaust chamber!
Would like to stay and talk but my wife is getting impatient with me as we are heading off!

[richban]

So Rob. Check out the frame. Look familiar? Yep its the one you had in your lockup. A good use for it I think.


So its been slow going for a we while due to actually having to do work but it is now ready for its first Shake down on the track.

This is the first 2 stroke I have built from split cases up. And it will not be the last. New Nitron rear shock on its way and also just a bit of mucking around to fit the Honda RS250 forks I have for it. But as it sits I have the correct weight springs and the front has been completely rebuild and working very well.

The ignitech is on and running but needs fine tuning. That will come when my connectors turn up to hook in the TPS and power Jets from the 38's

Also pipes. At the moment they are the tyga 250 pipes. They are a temp option but look rather nice and give good midrange but not so hot on the peak.

[Ocean1]

We are talking four strokes here of course and having to store the charge for one revolution (in the case of a single, - twin is different) - two strokes don't have to store it although I guess they do exactly that in the exhaust chamber!
Would like to stay and talk but my wife is getting impatient with me as we are heading off!

Subtle difference, yes. Although if 2 strokes didn't store compressed gas why do they need reed/rotary valves?

I suspect the largest issue with case-charged 4 strokes might be keeping the valve closed, you'd need damned near double the spring pressure.

[chrisc]

Subtle difference, yes. Although if 2 strokes didn't store compressed gas why do they need reed/rotary valves?

I hate to argue semantics because it's hardly worth doing but a disk valve allows asymmetric inlet timing, and they both ensure that the charge is pushed through the transfers rather than out the inlet. A two stroke doesn't need a reed valve or a disk valve to operate (piston port) but allows better control of the charge. Obviously there is compression taking place here but I thought I'd point that out as an answer to your rhetorical question.

[chrisc]

So Rob. Check out the frame. Look familiar? Yep its the one you had in your lockup. A good use for it I think.

Sorry I haven't been following. NSR250 frame right? With the 250 engine out to 300? Looks good!